<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>计数器</title>
  </head>
  <body>
    <input type="button" value="开始计数" onclick="startCount()">
    <input id="num" type="text">
    <input type="button" value="停止计数" onclick="stopCount()">
    <script>
      var timer = null, c = 0;
      function timedCount() {       // 在文本框中显示数据
        document.getElementById('num').value = c;
        ++c;                        // 显示数据加1
      }
      function startCount() {       // 开始间歇调用
        timer = setInterval(timedCount, 1000);
      }
      function stopCount() {        // 清除间歇调用
        clearInterval(timer);
      }
    </script>
    <p>
      <a href="file:///C:/Users/rise/Desktop/%E9%A6%96%E9%A1%B5/default/06.html">返回</a>
    </p>
  </body>
</html>